Controlling output voltage to achieve ultra-low standby power in dim-to-off LED applications

A flyback converter for powering an LED, comprising:

• a power switch transistor coupled to a primary winding of a transformer;
• a controller configured to control a switching of the power switch transistor to regulate a an output power to the LED during a lighting mode in which an output voltage to the LED is greater than an LED threshold voltage, and wherein the controller is further configured to regulate a light-off output voltage to the LED during a light-off state in which the output voltage to the LED is less than the LED threshold voltage, the controller including a controller power supply voltage input node for a controller power supply voltage coupled to an auxiliary winding of the transformer through a diode;
• and
• a power supply transistor coupled between the power supply voltage input node and an input voltage bus coupled to the primary winding;
• wherein the controller is configured to cycle the power supply transistor during a transition period to the light-off state to maintain the controller power supply voltage above an undervoltage-lockout (UVLO) voltage for the controller.